Electronic devices with moisture guiding structures

ABSTRACT

Electronic devices may have housings in which components are mounted. Some of the components may be sensitive to moisture. Other components may be insensitive to moisture and may form openings in a device housing that allow moisture to escape from within the housing. Components may be mounted on substrates such as printed circuit board substrates. Moisture repelling layers and moisture attracting layers may be patterned to form channels and other structures that guide moisture away from sensitive components towards insensitive components. Moisture repelling and attracting layers may also be used to limit the lateral spread of a conformal coating layer when coating components.

This application is a division of patent application Ser. No.12/871,804, filed Aug. 30, 2010, which is hereby incorporated byreference herein in its entirety. This application claims the benefit ofand claims priority to patent application Ser. No. 12/871,804, filedAug. 30, 2010.

BACKGROUND

This relates generally to electronic devices, and, more particularly, tomaterials within electronic devices that control moisture.

Electronic devices are often exposed to moist environments. As anexample, a user may operate a cellular telephone or media playeroutdoors when there is precipitation. Devices may also be exposed tomoisture in the form of perspiration.

Waterproof devices are able to withstand exposure to moisture.Waterproof housings are, however, often impractical for normal use.Conventional electronic devices are therefore vulnerable tomoisture-induced damage, particularly when sensitive device componentssuch as buttons are subjected to prolonged contact with moisture.

Conformal coatings are sometimes used to encapsulate device componentsand make them less vulnerable to moisture exposure. It can be difficult,however, to accurately control the application of conformal coatings,because conformal coatings often have a tendency to spread out over thesubstrates on which they are applied. Conformal coatings are also notalways effective at blocking moisture.

It would therefore be desirable to be able to provide electronic deviceswith improved configurations for protecting vulnerable device componentsfrom exposure to moisture.

SUMMARY

Electronic devices may have housings in which components are mounted. Anelectronic device may, for example, have buttons, input-output portconnectors, integrated circuits, displays, microphones, speakers,sensors, and other components.

Some of the components may be sensitive to moisture. For example,components such as buttons based on dome switches may be sensitive tothe presence of water.

Other components may be insensitive to moisture and may form openings ina device housing that allow moisture to escape from within the housing.For example, a data port connector may have input-output pins that arerelatively unaffected by small amounts of moisture and that may bemounted in an opening at the lower end of a device where moisture canexit the device.

During normal operation, a device may be exposed to moisture fromprecipitation or perspiration. The moisture may enter the interior ofthe housing of an electronic device through gaps. To prevent damage tosensitive components mounted within the device housing, moisturerepelling and attracting layers may be patterned on printed circuitboards, conformal coating layers, and other internal structures of thedevice.

For example, moisture repelling layers and moisture attracting layersmay be patterned on printed circuit board substrates with or withoutconformal coating layers to form channels that guide moisture away fromsensitive components towards insensitive components. Moisture repellingand attracting layers may also be used to limit the lateral spread of aconformal coating layer during the process of forming the conformalcoating layer over a sensitive component.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device inaccordance with an embodiment of the present invention.

FIG. 2 is a cross-sectional side view of a portion of an electronicdevice including a button and internal device components such as abutton switch and mounting structures in accordance with an embodimentof the present invention.

FIG. 3 is a cross-sectional side view of a conventional encapsulatedintegrated circuit showing how moisture can penetrate encapsulantpinholes.

FIG. 4 is a cross-sectional side view of a component such as anintegrated circuit that is covered with encapsulant showing howpatterned coatings may be used to prevent moisture damage in accordancewith an embodiment of the present invention.

FIG. 5 is a top view of an interior of an illustrative electronic deviceshowing how coatings can be patterned to create a moisture flow pathbetween a sensitive component region and an insensitive component regionin accordance with an embodiment of the present invention.

FIG. 6 is a diagram showing how coating patterning equipment may be usedto provide coatings with the ability to repel and attract liquids inaccordance with an embodiment of the present invention.

FIG. 7 is a cross-sectional side view of device structures that havebeen coated with patterned layers such as a liquid repelling coatinglayer in accordance with an embodiment of the present invention.

FIG. 8 is a cross-sectional side view of device structures that havebeen coated with patterned layers such as a liquid attracting coatinglayer in accordance with an embodiment of the present invention.

FIG. 9 is a cross-sectional side view of device structures that havebeen coated with patterned layers such as liquid attracting and liquidrepelling coating layers in accordance with an embodiment of the presentinvention.

FIG. 10 is a cross-sectional side view of device structures withpatterned liquid attracting and liquid repelling coating layers and apatterned interface layer in accordance with an embodiment of thepresent invention.

FIG. 11 is a top view of device structures including sensitive devicecomponents showing an illustrative pattern of liquid attracting andrepelling layers that may be used to prevent liquid from coming intoprolonged contact with sensitive device components in accordance with anembodiment of the present invention.

FIG. 12 is a top view of device structures including sensitive devicecomponents showing an illustrative pattern of liquid attracting andrepelling layers that may be used to create a multibranch channel forguiding liquid between a moisture entrance location and a moisture exitlocation that is away from the sensitive device components in accordancewith an embodiment of the present invention.

FIG. 13 is cross-sectional side view of a conventional conformal coatingthat is covering an integrated circuit on a printed circuit board.

FIG. 14 is a cross-sectional side view of a device component mounted ona substrate that has a patterned liquid repelling coating layer such asan oleophobic layer in accordance with an embodiment of the presentinvention.

FIG. 15 is a cross-sectional side view of the device component of FIG.14 showing how a conformal coating may be laterally constrained by thepatterned liquid repelling coating layer in accordance with anembodiment of the present invention.

FIG. 16 is a flow chart of illustrative steps involved in forming devicestructures that incorporate patterned liquid repelling regions andliquid attracting regions in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

Electronic device 10 of FIG. 1 may be a cellular telephone, mediaplayer, computer, handheld device, portable computer, tablet computer,Global Positioning System device, camera, gaming device, or otherelectronic equipment.

As shown in FIG. 1, device 10 may have a housing such as housing 12.Housing 12 may be formed from plastic, metal, carbon fiber compositematerial, other composites, glass, ceramics, other materials, orcombinations of these materials. Housing 12 may be formed from multiplepieces of material or may be formed using a unibody construction inwhich housing 12 is substantially formed from a single structure (e.g.,machined or cast metal, plastic, etc.).

Device 10 may have input-output devices such as input-output ports,speakers, microphones, displays, status indicator lights, touch screens,buttons, proximity sensors, wireless circuitry, accelerometers, ambientlight sensors, touch pads, and other devices for accepting input from auser or the surrounding environment of device 10 and/or for providingoutput to a user of device 10.

As shown in the illustrative configuration of FIG. 1, device 10 may, asan example, have a display such as touch screen display 14. One or morebuttons 16 may be used to gather user input. Buttons 16 may be based ondome switches or other switch circuitry. Buttons 16 may include buttonmembers that form push buttons (e.g., momentary buttons), sliderswitches, rocker switches, etc. Connector port 18 may be, for example, a30-pin connector for a 30-pin data port, a Universal Serial Bus port, orother input-output port. Port 19 may be, for example, a signal port suchas an audio jack for receiving an audio plug. Additional buttons such asbuttons 16, additional data ports such as port 18, and additional signalports such as audio connector port 19, and other input-output devicesmay be provided if desired. The example of FIG. 1 is merelyillustrative.

Devices such as device 10 may be vulnerable to moisture. For example,moisture may wick into gaps in device housing 12 or gaps betweeninternal device components. When moisture reaches sensitive devicecomponents such as button components, integrated circuits, or othercircuitry that is susceptible to malfunctions when wet, device 10 mayfail.

FIG. 2 is a cross-sectional view of a portion of device 10 in thevicinity of one of buttons 16. As shown in FIG. 2, button 16 may have abutton member such as button member 22 that reciprocates within opening20 of housing 12. When a user presses the exterior of button member 22in direction 24, portion 28 of button member 22 may press against a domeswitch or other switch mechanism in switch structure 30, therebyactivating the switch (e.g., shorting internal switch terminals togetherto close the switch). A dome member or other biasing element may pushbutton member 22 outward in direction 26 when the user releases pressurefrom button member 22.

A support bracket such as support bracket 32 may be used to mount switchstructure 30. To prevent moisture that has intruded into the interior ofdevice 10 from contacting switch structure 30, switch structure 30 maybe sealed from the interior (INT) of device 10 using flexible sheet 36.Sheet 36 may be formed from a moisture barrier material such as a layerof polyimide (e.g., a polyimide flexible printed circuit of the typethat is sometimes referred to as a flex circuit). Flex circuit 36 may beattached to bracket 32 using adhesive 38. Adhesive 38 may help form aseal between flex circuit 36 and nearby structures such as the interiorwalls of device housing 12 and internal housing member 34. Nevertheless,gaps may form such as illustrative gap 38, that allow moisture topenetrate region 40 adjacent to switch structure 30 from interior INT.Moisture may also penetrate region 40 through the gaps that are formedbetween the surface of button member 22 and the surrounding sidewalls ofopening 20 of housing 12.

Switch structure 30 may include a dome switch or other mechanism that isprone to failure if exposed to moisture (e.g., short term and/or longterm moisture exposure from water or other liquids). Switch structure 30therefore represents an example of a device component that exhibitssensitivity to moisture. Other moisture-sensitive device components mayinclude integrated circuits, discrete circuit components such asresistors, inductors, and capacitors, display structures, touch sensorcircuitry, and sensor circuits (as an example). These sensitive circuitsmay be vulnerable to moisture exposure due to weather conditions,perspiration, accidental spills, and other sources.

Other components in device 10 may be relatively insensitive to moisture.An example of a component that may be considered insensitive to moistureis connector 18. Connector 18 may contain input-output pins that receivea mating connector (e.g., a 30-pin plug on the end of a cable). Althoughconnector 18 may not be waterproof, it may be less likely to exhibit aserious failure than sensitive component such as one of buttons 16 whenexposed to moisture.

In environments such as these, it may be advantageous to control theflow of moisture within device 10. Coatings such as coatings that repeland attract moisture may be patterned to form regions of device 10 thatrepel moisture (e.g., regions that repel moisture away from sensitivecomponents) and regions that attract moisture (e.g., moisture guidingchannels that help route water away from sensitive components andtowards insensitive components). A moisture repelling coating may, forexample, be used to cover some or all of flex circuit 36 and gap 38 ofFIG. 2 to direct moisture away from gap 38. Components such as connector18 may not only be relatively insensitive to moisture, but may alsoserve as exit ports that allow moisture to escape from the interior ofhousing 12. Structures that guide moisture towards components such asconnector 18 may therefore help reduce moisture damage.

FIG. 3 is a cross-sectional side view of a conventional integratedcircuit mounting arrangement. As shown in FIG. 3, integrated circuit 46has been mounted on printed circuit board 44. Conformal coating 48 hasbeen used to cover integrated circuit 46. Conformal coating 48 may havea pinhole such a pinhole 50. When moisture 52 (e.g., water) comes intocontact with conformal coating 48, some of moisture 52 may penetratethrough coating 48 via pinhole 50. If moisture 52 reaches component 46,component 46 may fail.

FIG. 4 is a cross-sectional side view of a component mounting scheme ofthe type that may be used within device 10 of FIG. 1. As shown in FIG.4, component 60 may be mounted on substrate 58. Component 60 may be anintegrated circuit, a button (e.g., a dome switch for a button), orother sensitive device component. Substrate 58 may be a rigid printedcircuit board substrate (e.g., fiberglass filled epoxy such as FR4), aflexible polymer printed circuit board such as a polyimide printedcircuit board (i.e., a “flex circuit”), rigid flex, glass, ceramic, orother substrate. Device components can also be mounted on housingstructures and other structures in device 10.

Conformal coating 68 may be used to cover component 60. Conformalcoating 68 may be formed from materials such as epoxy, silicone,parylene, acrylic, polyurethane, other polymers, other dielectrics, etc.

To help prevent moisture 56 from reaching sensitive component 60 and tohelp control the lateral dimensions of conformal coating 68, patternedcoating layers such as layer 64 may be formed on substrate 58. Layer 64may include liquid repelling coating material and/or liquid attractingcoating material. As an example, material 64A may be formed from amaterial such as an oleophobic coating material that repels conformalcoating 68 and thereby constrains the lateral dimensions of coating 68and layer 64B may be a hydrophobic material that repels moisture 56(e.g., so that moisture 56 travels in direction 66). By preventingmoisture 56 from resting above pinhole 62 in conformal coating 68,moisture penetration to sensitive component 60 may be avoided orreduced.

Coating layers such as layer 64 may repel liquids such as water, liquidssuch as conformal coating materials, and other liquids (e.g., oils,adhesives, etc.). Coating layers such as layer 64 are sometimes referredto herein as hydrophobic layers (layers that repel liquids such as waterand potentially other liquids), hydrophilic layers (layers that attractliquids such as water and potentially other liquids), oleophobic layers(layers that repel oils and oily substances and that may potentiallyrepel other liquids and conformal coatings), and oleophilic layers(layers that attract oils and oily substances and that may potentiallyattract other liquids and conformal coatings). The properties of thesecoating materials need not be mutually exclusive. For example, ahydrophobic coating may also be oleophobic, a hydrophilic coating mayalso be oleophilic, etc.

Examples of hydrophobic materials that may be patterned to formpatterned hydrophobic coating layers include parylene, silicone, andpolytetrafluoroethylene. Materials such as these may also be oleophobic.Examples of hydrophilic materials that may be patterned to formpatterned hydrophilic coating layers include metal oxides (e.g.,titanium dioxide), materials in which metal oxide particles have beenincorporated within a binder, polyurethanes, and polyethylene oxide.Materials such as these may also be oleophilic. Surface treatments mayalso be used to form moisture attracting and moisture repelling regions.For example, a surface (e.g., a surface of one material or a surface ofmultiple materials) may be roughened to increase its hydrophilic andoleophilic properties or may be smoothed to decrease these properties.

Coating layers such as layer 64 may be applied and patterned byspraying, dipping, inkjet printing, painting, pad printing, screenprinting, shadow masking, lift-off, etc. Coating layers may be heated todry out the coating material and/or to thermally cure the material.Coating layers may also be cured by application of light and usingtwo-part chemical mixtures.

Layers such as layer 64 may be patterned to control the positioning andmovement of conformal coatings such as coating 68 and/or to control thepositioning and movement of moisture that intrudes into the interior ofdevice 10 such as water (e.g., from precipitation, from perspiration,etc.).

FIG. 5 is a top view of the interior of an illustrative electronicdevice. As shown in the example of FIG. 5, device 10 may have one ormore internal structures such as printed circuit boards, othersubstrates, and other mounting structures (e.g., parts of housing 12,etc.) that are mounted within housing 12 (i.e., the structures shown asbeing located within the rectangular boundary of housing 12 in FIG. 5).Sensitive components 72 (e.g., a sensitive component such as sensitivecomponent 60 of FIG. 4) may be mounted on these internal structures. Asensitive component such as button 16 may be mounted on internalstructures such as a printed circuit board or support structure throughan opening in a sidewall of housing 12.

Water may enter the interior of device 10 through a gap between button16 and housing 12. To prevent sensitive components 72 from becomingdamaged and to route the intruding water (or other moisture) away frombutton 16 and towards a safer location, coating layers may be patternedto form a moisture guiding structures. For example, region 70 and region78 may be coated with a moisture repelling layer such as a hydrophobiccoating. Region 74 may be coated with a moisture attracting substancesuch as a hydrophilic coating (or a coating that is at least lesshydrophobic than the coatings of regions 70 and 78). Dashed line 80represents the boundary between hydrophobic region 70 and hydrophilic(or at least less hydrophobic) region 74. Dashed line 82 represents theboundary between hydrophobic region 78 and hydrophilic (or at least lesshydrophobic) region 74.

Connector 18 may be a 30-pin data connector that mates withcorresponding 30-pin data connector 84 when connector 84 is moved indirection 86. Connector 19 may be an audio jack that receives audio plug88 when plug 88 is moved in direction 90. Connectors (e.g., connector18) may be less sensitive than components such as button 16 (e.g., adome-switch button) when exposed to water and other moisture. Connectorssuch as connector 18 may also serve as an opening (exit) that allowsinternal moisture to pass from the interior of device 10 to the exteriorof device 10. In this type of device environment, it may be desirable todirect moisture away from button 16 towards connector 18 (or, in robustaudio jack configurations, towards connector 19). This prevents themoisture from remaining near button 16, which is sensitive, and allowsthe moisture to reside instead near connector 18. The opening formed byconnector 18 may also allow the moisture to escape from device 10.

The pattern formed by regions 70, 74, and 78 may form a moisture-guidingpath (e.g., a path bounded by lines 80 and 82 and covering the areaoccupied by region 74). As indicated by arrow 76, the moisture-guidingpath may help guide moisture from button 16 to connector 18. Byencouraging moisture to move from the vicinity of button 16 to thevicinity of connector 18, potential device failures may be minimized.The use of hydrophobic coatings over regions 70 and 78 may also serve torepel moisture from underlying sensitive components 72.

FIG. 6 shows a system (system 92) in which tools 98 may be used to formpatterned coating layers for structures in device 10. Initially, nocoatings may be applied, as shown on the left of FIG. 6. In thisconfiguration, structures 94 and optional conformal coating 96 may beuncovered by additional coatings. Structures 94 may be substrates suchas printed circuit boards (flex circuits, rigid printed circuit boards,or rigid flex), components mounted on printed circuit boards (e.g.,integrated circuit packages), sensitive components such as component 60of FIG. 4 and components 72 of FIG. 5, other components, structures suchas internal housing structures, etc. Layer 96 may be a conformal coatingsuch as coating 68 of FIG. 4 and may include embedded sensitivecomponents such as component 60 of FIG. 4 and components 72 of FIG. 5.

As indicated by arrow 100, materials such as moisture attractingcoatings and moisture repelling coatings may be applied by tools 98.Following application of these materials, the surface of conformalcoating 96 (or, if conformal coating 96 is not present, structures suchas device components, substrates, etc.) may be covered with patternedlayers. The patterned layers may include moisture repelling layers suchas layer 64 (e.g., a hydrophobic layer). The patterned layers may alsoinclude moisture attracting layers such as layer 104 (e.g., ahydrophilic layer). Other layers such as layer 108 may also be formed.Layers such a layer 108 may be more or less hydrophobic than layer 64(or may be equally hydrophobic) and may be more or less hydrophilic thanlayer 104 (or may be equally hydrophilic). Uncoated regions such asuncoated surface 106 may also be formed. The water repelling and waterattracting characteristics of surface 106 are determined by the natureof the underlying material (i.e., coating 96 or the surface ofstructures 94 in configurations in which coating 96 is omitted).

FIG. 7 shows an illustrative arrangement in which hydrophobic layer 64is being used to repel water 56 so that water 56 moves to uncoatedregion 106 (e.g., in a situation in which uncoated region 106 on layer96 is more hydrophilic than layer 64 and when layer 64 is therefore morehydrophobic than region 106).

FIG. 8 shows an illustrative arrangement in which hydrophilic layer 104is being used to attract water 56 away from region 106 (e.g., in asituation in which layer 104 is more hydrophilic than uncoated surface106 of layer 96).

FIG. 9 shows an illustrative arrangement in which both hydrophobic layer64 and hydrophilic layer 104 have been formed on coating layer 96. Inthis situation, water 56 will be attracted away from layer 64 andtowards layer 104 because layer 104 is less hydrophobic and morehydrophilic than layer 64.

In the configuration of FIG. 10, an interface layer such as layer 114has been interposed between surface layers such as layer 64 and layer104. It may be difficult to adhere surface layers such as moisturerepelling layers to underlying layers such as layer 96. Interface layer114 may help form an adhesion promotion layer that helps surface layersbond to layer 96. Layer 114 may be formed from ink, polymer, or othersuitable coating materials.

Patterns of openings may be formed in the surface layers, interfacelayer 114, and coating layer 96 to expose surfaces such as surface 110of coating 96 (which may be hydrophobic) and surface 112 of structures94 (which may be hydrophobic). Using arrangements of this type, asubstrate such as a polyimide substrate (e.g., a flex circuit) such aslayer 94 may have mounted sensitive components that are covered withconformal layer 96 and/or conformal layer 96 may be omitted from all orsome of layer 94. Ink layer 114 may be patterned to form an adhesionpromotion layer for an a subsequent matching hydrophobic layer such aslayer 64. Polyimide is naturally hydrophilic, so the uncovered polyimidepattern in this arrangement forms a moisture-guiding channel bounded byhydrophobic region 64.

A top view of internal device structures that have been covered withpatterned layers of hydrophobic and/or hydrophilic materials is shown inFIG. 11. In the illustrative configuration of FIG. 11, moisture entersstructures 94 at entrance points IN. Moisture then flows in thedirection of arrows 116. Region 104 may be covered with a hydrophilicmaterial and region 64 may be covered with a hydrophobic material (i.e.,region 64 may be more hydrophobic and less hydrophilic than region 104).This pattern may therefore cause moisture to be deflected from paths 116towards exit location OUT along paths 118.

FIG. 12 shows an illustrative configuration in which the coating patternon structures 94 has been used to form a multibranch moisture guidingchannel (hydrophilic region 104) that is bounded by hydrophobic regions64. The channel may help guide moisture from moisture ingress points INtowards moisture exit location OUT.

FIG. 13 is a cross-sectional side view of a conventional conformalcoating 48 covering integrated circuit 46 on printed circuit board 44.As shown in FIG. 13, the surface of board 44 may attract conformalcoating 48, causing conformal coating 48 to spread significantly untilreaching relatively wide lateral dimension W.

FIG. 14 shows how moisture repelling coating material such as material64A may be formed around sensitive component 60 (e.g., a sensitivecomponent such as component 60 of FIG. 4). Material 64A may be providedin a layer that has the shape of a ring with a central rectangular orcircular opening (as examples). Material 64A may be formed from anoleophobic (hydrophobic) substance that repels conformal coating layer68. When layer 68 is deposited over component 60, the presence ofmaterial 64A ensures that layer 68 extends laterally only as far aslateral dimension N, as shown in FIG. 15. Lateral dimension N may besmaller than dimension W of FIG. 13 and/or may be more well controlledthan dimension W.

Illustrative steps involved in forming moisture repelling and moistureattracting layers in device 10 and/or in forming conformal coatinglayers in device 10 are shown in FIG. 16.

At step 120, a patterned layer such as layer 64A of FIG. 14 may beformed on a support structure such as substrate 58 (e.g., structures 94of FIG. 6). During the operations of step 120, a conformal coating layersuch as layer 68 of FIG. 15 may be formed over one or more sensitivecomponents 60. The presence of layer 64A (e.g., a hydrophobic and/oroleophobic layer) may limit the lateral spreading of conformal coatinglayer 68 (e.g., to help confine layer 68 to the region surroundingsensitive component 60).

At step 122, other device structures may be formed (e.g., by mountingsensitive components such as components 60 and 72 and other internalcomponents for device 10 to printed circuits boards, housing structures,ceramic substrates, glass substrates, underlying devices, and othersupport structures). These device structures may optionally be coatedwith conformal coating material (e.g., without using moisture repellinglayers such as layer 64A of FIG. 15).

During the operations of step 124, moisture repelling coatings may bedeposited and patterned (e.g., hydrophobic coating layers such as layer64 may be formed during the operations of step 126) and moistureattracting coatings may be deposited and patterned (e.g., hydrophiliccoating layers such as layer 104 may be formed during the operations ofstep 128). One, two, three, four, or more than four different regionsmay be formed, each having a potentially different respective amount ofhydrophobic and hydrophilic behavior. Tools 98 may be used in formingpatterned coating layers and/or layers such as conformal coating layer96. Techniques that may be used by tools 98 in forming layers duringstep 124 include spraying, dipping, inkjet printing, painting, padprinting, screen printing, shadow masking, lift-off, etc. Light may beapplied to cure deposited layers, lasers and other tools may be used topattern layers, layers may be heated to cure and/or dry materials, etc.

Following formation of the layers of step 124 (or earlier, in step 122or step 120), the patterned layers and underlying structures may bemounted in housing 12 of device 10.

A completed device (e.g., device 10 of FIG. 1) may be exposed tomoisture during normal operation (step 130). When exposed in this way,the moisture repelling regions on structures 94, the moisture attractingregions on structures 94, and the associated moisture-guiding channelsand other structures that are formed may help to guide and move moistureaway from buttons 16 and other sensitive device components and devicelocations towards connector 18 and other insensitive components anddevice locations.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention. Theforegoing embodiments may be implemented individually or in anycombination.

What is claimed is:
 1. An electronic device, comprising: a housing; atleast one electronic component mounted on a substrate in the housing; acoating on the substrate that surrounds the at least one electroniccomponent; a conformal coating that covers the at least one electroniccomponent and is laterally constrained by the coating that surrounds theat least one electronic component, wherein the conformal coating is indirect contact with the coating and wherein the conformal coating andthe coating are non-overlapping; and a hydrophobic coating that isformed in direct contact with the conformal coating, wherein thehydrophobic coating overlaps substantially all of the conformal coating.2. The electronic device defined in claim 1 wherein the coating on thesubstrate that surrounds the at least one electronic component comprisesan additional hydrophobic coating.
 3. The electronic device defined inclaim 2 wherein the at least one electronic component covered by theconformal coating is a moisture-sensitive electronic component.
 4. Theelectronic device defined in claim 3 further comprising: a connectormounted in the housing; and a patterned hydrophilic coating layer on thesubstrate, wherein the patterned hydrophilic coating layer forms amoisture guiding channel that directs moisture away from themoisture-sensitive electronic component towards the connector.
 5. Theelectronic device defined in claim 1 wherein the coating on thesubstrate that surrounds the at least one electronic component comprisesan oleophobic coating.
 6. The electronic device defined in claim 5wherein the at least one electronic component covered by the conformalcoating is a moisture-sensitive electronic component.
 7. The electronicdevice defined in claim 6 further comprising: a connector mounted in thehousing; and a patterned hydrophilic coating layer on the substrate,wherein the hydrophilic coating layer forms a moisture-guiding channelthat directs moisture away from the moisture-sensitive electroniccomponent towards the connector.
 8. The electronic device defined inclaim 1, wherein the hydrophobic coating is formed from a materialselected from the group consisting of: parylene, silicone, andpolytetrafluoroethylene.
 9. The electronic device defined in claim 8,wherein the coating on the substrate is formed from a material selectedfrom the group consisting of: parylene, silicone, andpolytetrafluoroethylene.
 10. The electronic device defined in claim 9,wherein the conformal coating is formed from a material selected fromthe group consisting of: epoxy, silicone, parylene, acrylic, andpolyurethane.
 11. An electronic device, comprising: a housing; a printedcircuit board in the housing; at least one moisture-sensitive electroniccomponent mounted to the printed circuit board; a coating on the printedcircuit board that surrounds the at least one moisture-sensitiveelectronic component; a conformal coating that covers the at least onemoisture-sensitive electronic component and is laterally constrained bythe coating that surrounds the at least one moisture-sensitiveelectronic component; and patterned coating layers on the printedcircuit board that direct water away from the at least onemoisture-sensitive electronic component and towards amoisture-insensitive component in the electronic device, wherein thepatterned coating layers include a patterned hydrophilic coating layeron the substrate, and wherein the patterned hydrophilic coating layerforms a moisture guiding channel that directs moisture away from the atleast one moisture-sensitive electronic component.
 12. The electronicdevice defined in claim 11 wherein the patterned coating layers comprisefirst and second portions of a hydrophobic coating layer, and whereinthe hydrophilic coating layer is bordered by and interposed between thefirst and second portions of the hydrophobic coating layer.
 13. Theelectronic device defined in claim 12 wherein the hydrophilic coatinglayer comprises a material selected from the group consisting of: metaloxide, material in which metal oxide particles have been incorporatedwithin a binder, polyurethane, and polyethylene oxide, and wherein thehydrophobic coating layer comprises a material selected from the groupconsisting of: parylene, silicone, and polytetrafluoroethylene.
 14. Anelectronic device, comprising: a housing; at least one electroniccomponent mounted on a substrate in the housing; a moisture-insensitivecomponent mounted in the housing; and a patterned hydrophilic coatinglayer on the substrate, wherein the patterned hydrophilic coating layerforms a moisture guiding channel that directs moisture away from the atleast one electronic component towards the moisture-insensitivecomponent.